RISC-V: Fix !CONFIG_SMP compilation error

Enabling both CONFIG_PERF_EVENTS without !CONFIG_SMP
generates following compilation error.

arch/riscv/include/asm/perf_event.h:80:2: error: expected
specifier-qualifier-list before 'irqreturn_t'

  irqreturn_t (*handle_irq)(int irq_num, void *dev);
  ^~~~~~~~~~~

Include interrupt.h in proper place to avoid compilation
error.
Signed-off-by: NAtish Patra <atish.patra@wdc.com>
Signed-off-by: NPalmer Dabbelt <palmer@sifive.com>

arch/riscv/include/asm/perf_event.h

@@ -10,6 +10,7 @@
 
 #include <linux/perf_event.h>
 #include <linux/ptrace.h>
+#include <linux/interrupt.h>
 
 #define RISCV_BASE_COUNTERS	2
 

arch/riscv/kernel/perf_event.c

@@ -27,7 +27,6 @@
 #include <linux/mutex.h>
 #include <linux/bitmap.h>
 #include <linux/irq.h>
-#include <linux/interrupt.h>
 #include <linux/perf_event.h>
 #include <linux/atomic.h>
 #include <linux/of.h>